Air heater with air flow sensing device



April 3, 1962 A. E. KRAUSZ AIR HEATER WITH AIR FLOW SENSING DEVICE 2 Sheets-Sheet 1 Filed Nov. 12, 1957 LL44; $4M

INVENTOR. Q/Zazz fin i i i April 3, 1962 A. E. KRAUSZ 3,027,889

AIR HEATER WITH AIR FLOW SENSING DEVICE Filed Nov. 12, 1957 2 Sheets-Sheet 2 Z. Z INVENTOR. 49 49 52/012 i faw BY j United States Patent M 3,027,889 AIR HEATER WITH AIR FLOW SENSING DEVICE Allan E. Krausz, The Siegler Corp, Centralia, 11]. Filed Nov. ,12, 1957, Ser. No. 695,814 3 Claims. (Cl. 126110) This invention relates to heating equipment, particularly to a control device for regulating the supply of fuel to the burners of heating equipment.

One object of the present invention is to provide a forced draft heater wtih a new and improved device for controlling the fuel flow and automatically reducing the fuel supply to a safe level in the event of failure of the forced air supply.

A more specific object of the invention is to provide an air sensing mechanism which has no pressure-responsive diaphragms, vanes, sail switches, or other moving parts in the air stream of the heater. In prior art heaters, such mechanisms have commonly employed pressure-responsive vanes and the like as, for example, shown in U.S. Patent Re. 22,276, reissued February 23, 1943, to Arthur N. Schreuder, and U.S. Patent No. 2,251,- 055, issued July 29, 1941, to David J. Howard, et al. The very small pressures utilized in supplying draft to a burner required that the prior art pressure-sensitive controls have relatively large vanes or diaphragms in the air stream to increase the force available to operate the control. However, the ungainly size of these vanes or diaphragms required excessive space. As a result of efforts to reduce the size of the vanes or diaphragms, these prior art controls proved unreliable and erratic in operation and were generally unsatisfactory in use. The present invention provides a control mechanism which is more positive and dependable in operation than types heretofore devised, has a minimum of linkage and moving parts, and is not subject to clogging by accumulation of foreign matter in the air ducts.

A further object of the invention is to provide a heater having the control device as indicated above operating entirely independently of all other control units of the heater, so that restoration of the forced air system will automatically render the heater responsive to the influence of its normal controlling devices without requiring any resetting by the operator.

Yet another object is to supply the correct amount of fuel and air to a cold burner automatically when initially starting the heater. The operator does not have to make a starting fuel setting and then wait until the burner becomes heated before making his desired operating setting. Failure to observe this waiting period before large quantifies of fuel are fed to a cold burner could cause an explosive mixture due to the puddling of the oil or incomplete combustion of the fuel.

Another object is to provide a device accomplishing these objects that is simple and rugged in design and construction, yet reliable and effective in operation.

The principles of the present invention are of particular advantage in warm air space heaters of the type having forced air supplied to the burner to provide sufficient oxygen to insure complete combustion and having forced circulation of heated air into the living area. The present invention provides for control of the fuel flow to the burner by an element sensitive to the movement of warm air in the outlet passage of the heater.

The unusual results following from this unique arrangement will be best understood in connection with the 3,027,889 Patented Apr. 3, 1962 FIGURE 2 is a detail cross-sectional view of the horizontal hot air duct of the unit, by which heated air may be projected in a horizontal stream across the surface of the floor upon which the unit is supported;

FIGURE 3 is an exploded view of the several component parts of the thermostat mechanism utilized in connection with the device;

FIGURE 4 is a plan view of the thermostat control head;

FIGURE 5 is a side elevational view thereof showing the control head of the thermostat atfixed to the oil valve of the heater with parts broken away and in section to illustrate the oil flow regulating valve;

FIGURE 6 is a detail sectional view taken substantially on the plane of the line 6-6 of FIGURE 4;

FIGURE 7 is a detail sectional view taken substantially on the plane of the line 77 of FIGURE 4.

FIGURE 8 is a sectional View taken along line 88 of FIGURE 4.

The forced air heater illustrated in FIGURE 1 of the present drawings is a home unit of the oil burning type having one blower to supply both the forced draft to the burner as well as circulating the heated air, although it will be understood that the principles of the present invention are equally applicable to heaters designed for other uses or using other types of fluid fuels. As illustrated, the heater consists of an exterior housing or shell having a front wall 10, back wall 1 1 and side walls of sheet metal which may be of wrap around construction, with the lowermost edges of the walls flanged at 12 and 13 to rest on a floor surface 14. The heater is preferably provided with an upper air grille 15 at the top and lower air grille 16 in the front wall adjacent the bottom of the unit. Under normal operation air is drawn inwardly through the upper grille, heated in the heat exchanger tubes, passed through the blower housing to the lower air duct, and directed outwardly through the lower grille.

The internal structure comprises a heating unit within the shell 10 and spaced from its walls by air spaces and suitable insulation, not shown. The heating unit includes a cylindrical fire pot 17 which, as shown, may be provided with disc-like baflies 18 and 19 arranged above a bottom plate 21 having an integral peripheral flange 22 fitted to the bottom of the cylindrical walls of the fire pot and thus forming an imperforate oil receptacle. The fire pot is surrounded by an air jacket 23 and a number of small air inlet ports 24 are provided in the peripheral walls 17 of the pot to permit inward flow of air from the jacket 23 to the fire. The fire pot 17 has its top plate 25 directly below a combustion chamber having a bottom 26, top 27 and vertical walls 28. An outlet connection 29 is provided at the top of the back wall for connection with a suitable flue.

A heat exchanger is provided within the combustion chamber. The heat exchanger includes a plurality of vertical air tubes 31 in side-by-side relation and extending between the top wall 27 and the bottom wall 26 of the combustion chamber. The upper ends of each of the tubes open to the air space 32 immediately below the upper air grille 15, and the lower ends of the tubes open into a rectangular air box 33 which is in turn connected to the inlet 34 of a centrifugal fan in a blower housing 35. The fan is driven by the motor 36 and the blower housing has an outlet passage 37 interconnected with the enlarged end of an air discharge duct 38 extending horizontally across the heater below the fire pot 17 and slightly above the floor surface 14 to deliver heated air (as shown by the arrow 44) to the lower grille 16 in the front wall 10. The air discharge duct 38 is provided with a branch conduit 39 leading to the air jacket 23 around the fire pot. In the preferred practice of the invention, a partial bafiie 41 is provided in the duct 38 to #3 direct a portion of the air from the blower into the fire pot jacket.

Fuel is supplied to the fire pot through an oil control valve housing 42 interconnected to the oil receptacle 21 of the fire pot by a feed pipe 43. The oil valve may be of any appropriate type, ordinarily having a float chamber fed from any appropriate oil supply, a regulating valve 70 (FIG. controlling the flow of oil to the burner, and a manually adjustable knob 45 to selectively determine the rate of flow from the chamber '72 through pipe 43 to the burner.

The fuel oil supplied to the burner thus flows through the feed pipe 43 into the fire pot, with the rate of flow of the fuel controlled or varied by the manually operable valve knob 45. The operation of the oil flow regulating valve 70 is subject, however, to overriding control by the device disclosed herein, arranged to bear on an auxiliary control pin 46 on the valve housing 42 (FIGURES 5 and 7) to restrict the valve to its minimum rate of fuel fioW in the event of any failure of the forced air supply, whether occasioned by power failure, blown fuse, motor burn out, or any other cause.

The present invention includes a device that is sensitive to the flow of heated air to control the oil flow, with a thermo-responsive bulb 47 in the duct 38 between the branch conduit 39 and the lower grille 16. The bulb is preferably mounted at an angle, with its capillary tube 48 extending from its lowermost end to a head assembly including a mounting plate 49 with a pressure-responsive element 52 riveted thereto. The mounting plate 49 is secured to the valve housing 42 by appropriate screws 51. The chamber of pressure element 52 is filled with thermostatic fluid surrounding internal bellows 53, supported by a backing screw 54 carried on a valve-actuator plate 55 pivoted on the plate 49 by a pin 56. The pressure-responsive element is arranged to lift the outer end of the rocker plate 55 against the force of the leaf spring 57 when the temperature-responsive bulb 47 is at normal operating temperature of the unit, but to permit the leaf spring 57 to rock the plate 55 in a counter-clockwise direction around the pivot 56 and press the control pin 46 downwardly whenever the bulb cools below a predetermined minimum temperature. In the event that the bulb 47, capillary tube 48 or bellows 53 should be damaged, the spring 57 will move the plate 55 downwardly and decrease the flow of the oil.

The blower and fuel metering valve may be interconnected in a manner well known in the art, so that the rate of air flow is proportioned by the rate of fuel flow when the valve is in any of its selected positions affording high fire for the burner,

The force circulation of air through the heat exchanger by operation of the blower is accompanied by increased air flow into the fire box and combustion chamber, and in normal operation the quantity of air passing through conduit 39 due to the blower action in forcing air through the output duct, is suflicient to combine with the maximum fuel delivered to the combustion chamber to insure complete combustion of the fuel.

If for any of a number of reasons, such as blower motor failure, power failure, or the blowing of a fuse, the blower ceases operation, the forced air supplied to the combustion chamber also ceases. If no overriding control of the fuel supply was provided, there would be no decrease in the supply of fuel fed to the combustion chamber, and the incomplete combustion resulting from the excess proportion of fuel to oxygen would allow soot to form and possibly allow unburned fuel fumes to leave the combustion chamber as well as the possibility of an explosive mixture forming in the combustion chamber when the blower starts again. The present invention provides this overriding control which reduces the fuel supplied to the chamber on any cessation of the blower operation. In this event, the lack of heated air passing over element 47 in the outlet results in the bulbs rapidly falling below the lower limit of operation of the control device, which may be about 110 F. As bulb 47 rapidly cools, it causes the fluid therein to contract, reducing the pressure in pressure-responsive element 52 allowing the bellows 53 to expand, thus causing the plate 55 under pressure of spring 57 to press the valve pin 46 downwardly into low fire position. Sufficient oxygen is available for complete combustion of the fuel delivered to the combustion chamber when the metering valve is in its low fire position.

The heater will operate in this low fire position until the cause of the blowers ceasing operation is remedied irrespective of the setting of the manual knob 45. Upon blower resumption, hot air is again forced over the element 47, expanding the fluid therein to lift the plate 55 from the control pin 46. This removes the overriding control of the safety control and restores regular heater operation, with normal control of the metering valve by the manual adjusting knob 45.

It will be obvious to those skilled in that art that although I have described an adaptation of the invention as applied to the well known constant level valve, the invention may be carried out by the use of a separate warm air responsive valve placed at any suitable point in the fuel line.

It will also be evident that the simple hydraulic valve actuator may be used to operate an electric switch which in turn may control an electric circuit to a solenoid valve without avoiding the scope of invention.

It is seen that the present invention functions to reduce the fuel oil fed to the burner automatically upon any cause of blower failure, by sensing the cessation of the heated air flow, and also functions to restore full heater operation when the blower action resumes.

This achieves important new results in several respects. For one thing, the warm air sensing element renders the fuel control apparatus sensitive to the flow of air through the circulatory system of the heater without the need of pressure-sensitive diaphragms, sail switches or other prior conventional air-responsive devices. It follows that the disclosure of the present invention is much less subject to malfunction or failure of operation than any apparatus employing moving parts in the air stream, where their movement may be impeded by accumulation of dust or lint. The prior conventional air sensing devices are erratic and unreliable in operation due to their inherent size and lack of sensitivity. With the present invention, high reliability and dependability of control may be achieved.

Having thus described my invention, what I claim as new and desire to secure by United States Letters Patent 1. A heater and control system therefor comprising a combustion chamber, a pot type burner within said chamber which is adapted to operate on a low fire and a high fire, means for supplying fuel to said burner including flow regulating means for controlling the amount of fuel being supplied to said burner from low rate to high rate to provide from low to high fire, and means for overriding said regulating means to selectively provide said low fire and permit said high fire at the burner, a heat exchanger communicatively associated with said combustion chamber, conduit means beneath the burner and heat exchanger in fluid communication with said heat exchanger and terminating at one end in a hot air exhaust opening at the outer surface of the heater, blower means disposed in communication with said heat exchanger and said conduit means and operative to cause air to flow downwardly through said heat exchanger and out the exhaust opening in said conduit means, means shunting a portion of the flow of air from said conduit means to said burner and affording natural draft to said burner when said blower means is inoperative, an air-flow sensing device comprising a thermo-sensitive element disposed in said conduit means in shielded relation to the radiant heat from said burner, said sensing device being operatively connected with said overriding means so that temperature of the air in said conduit surrounding said element below that provided by the low fire with the blower means in operation causes said overriding means to provide said low rate, and so that temperature of said air in said conduit surrounding said element and equal to that provided by low fire with said blower means in operation causes said overriding means to permit supply of fuel at said high rate.

2. A heater and control system therefor comprising a combustion chamber, a pot type burner within said chamber which is adapted to operate on low fire and high fire, means for supplying fuel to said burner including flow regulating means for controlling the amount of fuel being supplied to said burner from low rate to high rate to provide from low to high fire, and means for overriding said regulating means to selectively provide said low fire and permit said high fire at the burner, a vertically extending heat exchanger communicatively associated with said combustion chamber, conduit means in communication with said heat exchanger and disposed at a lower level than said burner and heat exchanger, said conduit means terminating at one end in a hot air exhaust opening at the outer surface of the heater, blower means disposed in communication with said heat exchanger and said conduit means and operative to cause air to flow downwardly through said heat exchanger and out the exhaust opening of said conduit means, means connected between said conduit means and said combustion chamber for shunting a portion of the flow of air in said conduit means to said burner and for affording natural draft in said combustion chamber when said blower means is inoperative, and an air-flow sensing device comprising a thermo-sensitive element disposed in said conduit means adjacent said exhaust opening, said sensing device being operatively connected with said overriding means so that temperature of the air in said conduit surrounding said element below that provided by the low fire with the blower means in operation causes said overriding means to provide said low rate, and so that temperature of the air in said conduit surrounding said element and equal to that provided by low fire with said blower means in operation causes said overriding means to permit supply of fuel at said high rate.

3. A heater and control system therefor comprising a combustion chamber, a pot type burner in said chamber which is adapted to operate with natural draft flow of air at a low flame level and with forced draft at a high flame level, means for supplying fuel to said burner in eluding flow regulating means for controlling the amount of fuel supplied to said burner from low rate to high rate to provide from low flame to high flame level, and means for overriding said regulating means to selectively provide said low flame and permit said high flame level at the burner, an indirect heat exchange system communicatively associated with said combustion chamber and comprising a vertically extending heat exchanger including a plurality of tubes having communication at their upper ends with the air space above the upper portion of said combustion chamber, conduit means disposed below said combustion chamber and in communication with the lower ends of said tubes, said conduit means terminating in an exhaust opening at the outer surface of the heater, and a blower associated with said heat exchanger and conduit means which is adapted to effect a flow of air downwardly through said tubes and out said exhaust opening, additional conduit means communicatively connected between said first mentioned conduit means and said burner in said combustion chamber to provide a gravity flow of air into said chamber through said exhaust opening when said blower is inoperative and to shunt a portion of the flow of air from said blower to said chamber when said blower is operative, and an air flow sensing device comprising a thermo-sensitive element disposed in said first mentioned conduit means between said exhaust opening and said additional conduit means and in a shielded position relative to said burner, heat exchanger, and combustion chamber, said sensing device being operatively connected with said overriding means so that air temperature in said first conduit means surrounding said thermo-sensitive element below that provided therein by the low flame level with the blower in operation causes said overriding means to provide said low rate, and so that temperature of the air in said first conduit means which is equal to or greater than that provided by low flame operation with said blower means in operation causes said overriding means to permit the supply of fuel at said high rate.

References Cited in the file of this patent UNITED STATES PATENTS 1,681,421 McCabe Aug. 21, 1928 1,985,799 Scheifele Dec. 25, 1934 2,157,109 Bell May 9, 1939 2,282,197 Maynard May 5, 1942 2,331,219 Mueller et al. Oct. 5, 1943 2,356,705 Siegler et al Aug. 22, 1944 2,428,867 De Lancey Oct. 14, 1947 2,477,804 Huber Aug. 2, 1949 

